Photosensitive opal glass



y 3, 1950 s. D. STOOKEY 2,515,941

PHOTOSENSITIVE OPAL GLASS Filed Sept. 9, 1946 INVENTOR. Jrn/vz [x 001mmJraa/rn' 14770 k/g y patented juiy 18, 1956 UNITED STATES PATENT OFFICEPHOTOSENSITIVE OPAL GLASS Stanley Donald Stookey, Corning, N. Y.,assignor to Corning Glass Works, Corning, N. Y., a corporation of NewYork Application September 9, 1946, Serial No. 695,802

This invention relates to photosensitive glasses, that is, glasses inwhich exposure to short wave radiations, 400 millimicrons or less, bringabout an invisible change as a result of which irradiated areas arecapable of heat developed coloration while non-irradiated areas remainsubstantially unchanged on heating.

In pending applications Serial Nos. 513,441, 513,443 and 513,444,.filedDecember 8, 1943,there are described colorless photosensitive glasses inwhich a colored photographic image may be formed by exposure through asuitable negative followed'by heating the glass. In such glasses thecontrast between high lights .and low lights is a variation in thedensity of the color of the lightaffected areas of the glass.

In my pending application serial No. 513,445 filed December 8, 1943, Ihave described colorless photosensitive glasses in which a colored'photographic image likewise may be formed and developed by suitable exposurethrough a negative and subsequent heating but which become opacifiedthroughout during heating to provide a white opaque background for thecolored image.

The primary object of this invention is to provide photosensitiveglasses in which only the developed image is opaque or glasses in whichlightaffected areas become opacified on heating while unexposed areaswith the same heat treatment compositions in which selective irradiationand subsequent heating produce in "the glass an opaque image by thedifierential precipitation of either lithium disilicate or bariumdisilicate in-' the irradiated areas during heating. "To cause suchselective precipitation of the opacifying'dis-ilicate particles it isnecessary to incorporate into the glass one of the photosensitizingmetals, gold, silver or copper, employed in the glasses of the abovementioned patent applications. These make the glass sensitive to shortwave radiations and on subsequent heating of the glass they provide'colloidal nuclei for the formation and growth of the opacifying'crystallites. In another application Serial No. 695,801'filed by meconcurrently herewith Ihave described and claimed photosensiti-veglasses and articles in which the image forming crystallites are lithiumdisilicate. The present application is specifically directed to glassesand articles in which photographic images are formed by the{differential precipitation of barium disilicate.

13 Claims. (Cl. 49-92) The glasses of the present invention containsitizing agent. Silver and copper are not effective. m0 may besubstituted wholly or in part for Nan). Additionoi A1203, B203 or oxidesof the second periodic group other than BaO generally tends'topreventopacification or precipitation of barium disilicate duringheating of the glass. However, small percentages of one or more of theseoxides may be employed to control excessive opacification andto extendthe working range of the glass. Up 4% A1203, or up to 3% of B203 or caoor MgO 01' 2M), or up to 12% SrO may thus be employed.

The new glasses are transparent and un'colored by the gold whenfabricated, but when exposed to short wave radiations and subsequentlyheated, the exposed areas become opacifid by the precipitation of bariumdisilicate but unexposed areas remain clear. The minimum amount of goldwhich is efiective to induce opacification 0f the exposed areas is about.004% Au. The opacification of the exposed areas is progressivelyintensified by increasing the amount of gold. Maximum opacihcation isproduced by about .05% Au. Maximum cpacification is also produced bylarger amounts, but their use is impractical for economic reasons. Theexposed and opacified areas may be colored by the gold if a sufilcientamount within or above the above recited range is used and if theirradiation and subsequent heat treatment of the glass are sufficientlyintense or prolonged, as will laterappear. The colors obtained may varyfrom blue through lavender and pink to red. Under conditions whichproduce coloration, the opacification oi the irradiated areas of theglass, occurs subsequent to their coloration. The goldis preferablyintroduced into the batch as a solution of gold in acid to form goldchloride.

In general, the use of gold as as'ensitizing metal in the new glasses issubject to the samefconsiderations and limitations which attend its useinthe glasses disclosed in my pending application Serial No. 513,443referred tdabove'. Photosensitivity of the new glasses is. prevented bythe presence of reducing agents and isprevented or objectionably,dfminished by the presence of substantial a unts of comp unds ,oia senil ad. h l iu vanadium, uranium, iron, manganese or selenium.

Cerium in small amounts intensifies the photosensitivity of the newglasses, that is, it increases the effect of a given exposure orshortens the time of exposure necessary to produce a given effect. Inlarge amountsit decreases or prevents. the photosensitivity of theglass. The maximum intensifyingeffect of cerium occurs in glassescontaining about 134% CeOz and not more than .05 CeOa should beemployed.

Theaddition of up to .'03% SD02 or SbzQs tends to preventa blue and topermit only a red coloration to develop in the surface of the irradiateda a f t clas du ng h a n b d vr lqa '3 ment of opacity in the same areasubsequently occurs only below the surface where the glass has notbecome red. This results in a transparent.

red image superimposed on a white opaque image.

The density of the coloration in the presence of SnOz or $10,203increases with increasing gold content and the depth to which thecoloration extends or penetrates into the glass increases withincreasing time of exposure of the glass to short wave radiations.

Coloration of the irradiated areas of the glass by the gold duringheating may be prevented by using an amount of gold too small to producecoloration, though sufilcient to produce opacification, or by employinglarger amounts of gold and using an exposure time or intensitysufiicient to bring about opacification but insufiicient to permit avisible coloration to develop on heating. Such exposure conditions varyfor different compositions but may readily be determined by trial.

The temperature for the development of opacification is somewhat higherin a given glass than for the development of the color of the gold andis about 100 C. or less below the softening point of the glass.Coloration without opacification may therefore be produced by usingtemperatures high enough to cause coloration of the exposed areas butnot high enough to cause opacification thereof.

From the foregoing description it will be seen that various effects canbe produced by means of the invention. Such effects include whiteopacified images or designs, colored opacified images or designs, and acolored but unopacified image or design in the surface of the glasssuperimposed on an identical opacified image or design within the bodyof the glass, any one or all'of which can be produced in a single glassarticle.

The accompanying drawing illustrates articles made in accordance withthe invention.

Fig. 1 is a plan view of a glass panel In in which light-diffusing oropacifying microscopic crystal lites of barium disilicate areprecipitated in the glass to form a white opaque design comprising blockletters ll, l2 and 13, the glass being otherwise clear and colorless.

Fig. 2 is a sectional view on an enlarged scale on line 22 of Fig. 1showing that the opacifying crystallites forming the design are presentthroughout the thickness of the glass so that the design isthree-dimensional and extends completely through the glass panel.

Fig. 3 is an enlarged sectional view of a glass panel similar to thatshown in Fig. 2 and containing a design comprising block letters as inFig. 2 which are opaque white in the section designated H1 at the backof the panel, and are a transparent red color in the section designated15 at the front of the panel.

The following batches in parts by weight are given as examples toillustrate but not to limit my invention:

SiOz 100 100 100 100 100 NazCOa. 14. 3 14. 3 l4. 3 40. 7 25. 7 22 NaNO:4. 7 4. 7 4. 7 5. 6 4. 7 4 KzC03 17.7 17.7 17.7 BaCOa. 55. 55. 5 55. 586. 4 42. 7 36. 6 A1(OH)3 5.0 5.0 5.0

ricated in the usual manner, they produce substantially transparentglasses which, when exposed to short wave radiations and subsequentlyreheated, will become opacified in the exposed areas but will remainunchanged in the unexposed areas. Composition 1 is particularly suitablefor my purpose and when melted it results in a glass which consistsapproximately of SiOz, 6% NazO, 6%K2O, 26%Ba0, 2% A1203, .04% C802, 02%SbzOs, and .0075% Au.

The proper time of exposure and subsequent heat treatment of the newglasses will depend upon the gold content, the character and intensityof the light source and the color effects desired. In general whenplates 01' glass made from the above compositions are exposed from 1 to10 minutes, either directly or through a suitable photographic negative,at a distance of 14 inches from a 60 ampere carbon arc using 0 carbonelectrodes (manufactured by The National Carbon Company), and aresubsequently heated for 10 minutes to an hour or more at 600 to 700 C.,an opacification will be developed in the irradiated area of the glasswhile the unexposed portion will remain clear. If the exposure is madethrough a photographic negative, the opacification will form a positiveimage in minute detail in the glass. More specifically for example,composition 1 will develop a white opal with a two minute exposurefollowed by heating for a few minutes at 700 C. With a five minuteexposure the color is blue; with a 20 minute exposure the color islavender and with a 40 minute exposure thecolor is' pink. Thepenetration of the color and the opacity into the glass increase withthe time of exposure. Composition 5 will develop a translucent opalwhich is faintly blue when exposed for ten minutes and heated at 700 C.With an exposure of one hour followed by heating for a few minutes at700 0., a strong opacification is developed which is colored blue. Ineach case the unexposed portion of the glass remains clear and unchangedin color during heating.

The effect of the irradiation and the image produced by heating theirradiated glass extend from the surface into the glass usually to adepth of 1 to 5 mm. or more, depending upon the time and intensity ofexposure and the gold content and being greater as the exposure or thegold content is increased.

X-ray diffraction patterns of the new glasses after irradiation and heattreatment show that crystalsof barium disilicate are present in theopacifie d areas but are not present in the clear or unopacified areas.:Such crystals are microscopic in size and are precipitated during theheat treatment.

Ultravioletemitting lamps, such as the carbon are or the quartz mercuryarc, are convenient sources of radiations which are effective for mypurpose, but treatment with X-rays, radioactive radiations and. othersources of radiations shorter than 400 millimi'crons is included withinthe scope of the present invention.

The new glasses are useful for many purposes such as: illuminating wareof various kinds, signalling devices, headlights, windows, etc., in

which transverse, opaque or translucent ribbons withinthe otherwiseclear glass are employed as louvres' to transmit direct light in somedirections but to cut off or transmit only diffused light in others;illuminated decorative photographs,

block-letter signs, etc., wherein three-dimension- When the abovebatches are melted andfaba1 light-scattering images are employed to proati 6,5 11

. 5 due-e unique eif'ects"fwith oblique 'iuumi atiou; hotographic opaldesigns in glass tableware; durable, permanent images forpi'ojection,asin lantern slides; making such articles the de sired designs,transverse louvife's, images, 'etc., are produced in the glass byirradiation thereof through appropriate photographic negatives followedby uniformly heating thegl'as's throughout as set forth above.- I i i IThe term silicate glass, as used in thecl aims, means a glass preparedby fusion of raw glassmaking materials under non-reducing conditionscontaining, on the oxide basis, a major pro on tion of silica and aminor proportion of an alkali metal oxide such as sodium oxide orotassium oxide and a minor proportion of barium oxide, and optionallycontaining a minor proportion of one or more other conventionalglass-forming oxides such as A1202, B20301 an oxide of a metal of thesecond periodic group other than barium,

but being free of constituents which inhibit photosensitivity includingcompounds of arsenic, lead, thallium, vanadium, uranium, iron,manganese, and selenium and also over 4% A1202, over 3% B203 or CaO orMgO or ZnO, and over 12% SrO.

I claim:

1. A photosensitive glass consisting essentially of a silicate glasscontaining, on the oxide basis by weight, 50% to 65% Si02, 5% to 15% ofan alkali metal oxide selected from the group consisting of Na20, K20,and mixtures of Na20 and K20, 15% to 45% BaO, 0.004% to 0.05% of goldcomputed as Au, and up to 0.05% Ce02.

2. A photosensitive glass consisting essentially of a silicate glasscontaining, on the oxide basis by weight, 50% to 65% S102, 5% to 15% ofan alkali metal oxide selected from the group consisting of Na2O, K20,and mixtures of Na2O and K20, 15% to 45% BaO, 0.004% to 0.05% of goldcomputed as Au, and up to 0.03% Sn02.

3. A photosensitive glass consisting essentially of a silicate glasscontaining, on the oxide basis by weight, 50% to 65% S102, 5% to 15% ofan alkali metal oxide selected from the group consisting of Na20, K20,and mixtures of Na20 and K20, 15% to 45% BaO, 0.004% to 0.05% of goldcomputed as Au, and up to 0.03% 513203.

4. A photosensitiveglass consisting essentially of a silicate glasscontaining, on the oxide basis by weight, 50% to 65% Si02, 5% to 15% of,an alkali metal oxide selected from the group consisting of Na2O, K20,and mixtures of Na20 and K20, 15% to 45% BaO, 0.004% to 0.05% of goldcomputed as Au, up to 0.05% 0e02, and up to 0.03% SbzOa.

5. An article comprising a body of irradiated substantially colorlessphotosensitive glass consisting essentially of a silicate glasscontaining,

on the oxide basis by weight, 50% to 65% Si02,

5% to 15% of an alkali metal oxide selected from the group consisting ofNa20, K20, and mixtures of Na and K20, 15% to BaO, and 0.004% to 0.05%of gold computed as Au, said glass body containing within its mass apredetermined latent photographic image capable of being developed, byuniform heating of the entire glass body, into a visible opacified imageexhibiting photographic detail and comprising light-diffusingcrystallites of barium disilicate.

6. An article comprising a body of irradiated, substantially colorlessphotosensitive glass consisting essentially of a silicate glasscontaining, on the oxide basis by weight, to S102, 5% to 15% of analkali metal oxide selected from tiiejg 'rqi p ccnsisting er Na'20, K26,and of nine and K20, 15% to 45% Eat), 0.004% to 0.05% of gold computedas Au, and up to 0.05% 0e02, said glass b'ody containing within its m ssa predetermined latent photographic image 102, pableo'i being developed,by uniform heating of the entire glass body, into a visible, opacifiedimage exhibiting photographic detail and 0on1- prising light-'difiu'singcrystallites of barium disilicate.

'7. An article comprisinga body made of a photosensitive glassconsisting essentially of a silicate glass containing, on the oxidebasis by Weight, 50%to 65% S102, 5% to 15% of an alkali metal oxideselected from the group consisting of NarO, K20, and mixtures of Na20and K20, 15% to45% BaO, and 0.004% to 0.05% of gold computed as Au,selected portions of said glass body containing light-diffusingcrystallites of barium disilicate in quantity and arrangement to formwithin its mass a heat-stable, opaque image exhibiting photographicdetail.

8. An article comprising a body made of a photosensitive glassconsisting essentially of a silicate glass'containing, on the oxidebasis by weight, 50% to 65% Si02, 5% to 15% of an alkali metal oxideselected from the group consisting of Na20, K20, and mixtures of Na20and K20, 15% to 45% BaO, 0.004% to 0.05% of gold computed as Au, and upto 0.05% 0e02, selected portions of said glass body containinglight-diffusing crystallites of barium disilicate in quantity andarrangement to form within its mass a heatstable, opaque imageexhibiting photographic detail.

9. An article comprising a body made of a photosensitive glassconsisting essentially of a silicate glass containing, on the oxidebasis by weight, 50%to 65% S102, 5% to 15% of an alkali metal oxideselected from the group consisting of Na2O, K20, and mixtures of Na20and K20, 15% to 45% BaO, 0.004% to 0.05% of gold computed as Au, and upto 0.03% Sn02, selected portions of said glass body containinglight-diffusing crystallites of barium disilicate in quantity andarrangement to form within its mass a heat-stable, opaque imageexhibiting photographic detail.

10. An article comprising a body made of a photosensitive glassconsisting essentially of a silicate glass containing, on the oxidebasis by weight, 50% to 65% Si02, 5% to 15% of an alkali metal oxideselected from the group consisting of Na20, K20, and mixtures of Na20and K20, 15% to 45% BaO, 0.04% to 0.05% of gold computed as Au, and upto 0.03% SbzOa, selected portions of said glass body containinglight-diffusing crystallites of barium disilicate in quantity andarrangement to form within its mass a heat-stable, opaque imageexhibiting photographic detail.

11. An article comprising a body made of a photosensitive glassconsisting essentially of a silicate glass containing, on the oxidebasis by weight, 50% to 65% S102, 5% to 15% of an alkali metal oxideselected from the group consisting of Na20, K20, and mixtures of Na20and K20, 15% to 45% BaO, 0.004% to 0.05% of gold computed as Au, up to0.03% Sb202 and up to 0.05% 0e02, selected portions of said glass bodycontaining light-diffusing crystallites of barium disilicate in quantityand arrangement to form within its mass a heat-stable, opaque imageexhibiting photographic detail.

12. An article comprising a body made of a photosensitive glassconsisting essentially of asilicate glass containing, on the oxide basisby Wei ht, 50% to 65% SiOz, to 5% o n a i metal o iiide selected fromthe group consisting of NazO, K20, and mixtures of NazO and Kz O, 15% toBaO, and 0.004% to 0.05% of gold computed as Au, selected portions ofsaid glass body containing light-diffusing crystallites of bariumdisilicate in quantity and arrangement to form within its mass aheat-stable, opaque image exhibiting photographic detail, andsuperimposed on said opaque image and in register therewith acolored,unopacified image. f

13; The method of making a glass article which comprises forming anarticle of a photosensitive glass consisting essentially of a silicateglass containing, on the oxide basis by weight, to SiOz, 5% to 15% of analkali metal oxide selected from the group consisting of N a2O, K20, andmixtures of NazO and K20, 15% to 45% -BaO, and 0.004% to 0.05% of goldcomputed as Au, exposing an area of the article to short-waveradiations, and thereafter heating the article uniformly for a time andat a temperature sufiicient to cause precipitation of barium disilicatecrystallites in the exposed area.

STANLEY DONALD STOOKEY.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Certificate of Correction Patent No. 2,515,941July 18, 1950 STANLEY DONALD STOOKEY It is hereby certified that errorappears in the printed specification of the above numbered patentrequiring correction as follows:

Column 6, line 54, for 0.04% read 0.004%

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the case in the PatentOffice.

Signed and sealed this 7th day of November, A. D. 1950.

THOMAS F. MURPHY,

Assistant Commissioner of Patents.

5. AN ARTICLE COMPRISING A BODY OF IRRADIATED SUBSTANTIALLY COLORLESSPHOTOSENSITIVE GLASS CONSISTING ESSENTIALLY OF A SILICATE GLASSCONTAINING, ON THE OXIDE BASIS BY WEIGHT, 50% TO 65% SIO2, 5% TO 15% OFAN ALKALI METAL OXIDE SELECTED FROM THE GROUP CONSISTING OF NA2O, K2O,AND MIXTURES OF NA2O AND K2O, 15% TO 45% BAO, AND 0.004% TO 0.05% OFGOLD COMPUTED AS AU, SAID GLASS BODY CONTAINING WITHIN ITS MASS APREDETERMINED LATENT PHOTOGRAPHIC IMAGE CAPABLE OF BEING DEVELOPED BYUNIFORM HEATING OF THE ENTIRE GLASS BODY, INTO A VISIBLE OPACIFIED IMAGEEXHIBITING PHOTOGRAPHIC DETAIL AND COMPRISING LIGHT-DIFFUSINGCRYSTALLITES OF BARIUM DISILICATE.